GEOLOGICAL SOCIETY OF LONDON. 



25 



The Secretary read a letter addressed by Mr. Lyell to Dr. 

 Fitton, containing remarks " on some of the Phenomena C07i- 

 nected with the coal measures and older strata of Penn- 

 sylvania'' 



Mr. Lyell's attention, from the period of his arrival in 

 America to the date of this communication (1 5th October), 

 had been principally devoted to the great succession of 

 Silurian, Devonian, and Carboniferous rocks of Pennsylvania 

 and New York, but he confines his present remarks more 

 particularly to the phenomena presented by the coal mea- 

 sures, and the extension to America of Mr. Logan^s gene- 

 ralisations respecting the beds of fire-clay containing Stig- 

 maria, which occur beneath each stratum of coal in tlie 

 Glamorganshire coal-field. Mr. Lyell first visited the col- 

 lieries of Blossberg, on the extreme northern frontier of 

 Pennsylvania, and in the examination of which he was as- 

 sisted by Dr. Saynisch, President of the Mines. The strata, 

 both in detail and as a whole, bear an exact analogy to the 

 British coal measures, and he found beneath every seam, 

 except one, a bed of fire-clay, varying from one to six feet 

 in thickness, and containing abundance of Stigmaria, with 

 their leaves attached to the stem. All the specimens seen 

 in situ, with one exception, were parallel to the planes of 

 stratification, but the leaves penetrated the clay in all direc- 

 tions. The roof of the coal seams is usually composed of 

 bituminous shales, but sometimes of very micaceous grits 

 which afford a great variety of ferns and other plants, all of 

 them agreeing, generally, at least, with those common in 

 British coal measures. Mr. Lyell afterwards examined the 

 anthracite deposits at Pottsville, in the southern part of 

 the Alleghanies, under the guidance of Professor H. D. 

 Rogers , also the coal-field of Tamaque, the I^ehigh summit 

 mine, the Room Run Mines, on the Nesquahoning, and the 

 Beacon Meadow, or middle coal-field — in all of which dis- 

 tricts he found beneath each coal seam a bed of fire-clay 



